Catalyst and methods of making same



United States Patent Ofiice Patented July 19, 1955 No Drawing.Application March 26, 1951, Serial No. 217,667

6 Claims. (Cl. 252-435) This invention relates to the manufacture anduse of catalysts particularly of the solid granular type which aresuitable for organic reactions generally, polymerizing reactionsspecifically and more particularly for the polymerization of olefins toproduce liquids from gaseous hydrocarbons and/or to increase themolecular weight of the compounds so treated. This application is acontinuation-in-part of my application Serial No. 784,516, filedNovember 6, 1947,, issued as Patent Number 2,586,852.

In one specific embodiment the present invention relates to the use ofmixtures of phosphoric acids and china clay or kaolin in admixture forthe treatment of olefins hlydi'ocarbons to polymerize the samethe mixture of china clay and phosphoric acids being heated or baked to bringabout hardening by combined chemical reactions and removal of water. Theacid may comprise 25 to 75% and more of the final weight of thecatalyst.

The phosphoric acids employed are preferably the orthophosphoric and/orpyrophosphoric acids or mixtures of the same; which may also contain, ifdesired, some free P205, preferably to a thick syrupy consistency. Thechina clay which contains about 14% moisture mixes readily with the moreconcentrated acids up to 100% orthophosphoric or above. The heavy pastemay be formed by extrusion or otherwise into suitable shapes and sizes.

The formed catalyst is then dried or baked at temperatures varying from400 to 600 F. depending on the time it is so heated, concentrations ofacids, etc. The lower range may be employed by the special modificationswhich I disclose herein to produce the catalyst directed to lowtemperature quick hardening.

The relatively inert material which. may be used in my invention ischina clay or kaolin (also sometimes referred to as kaolinite) whichterms I shall employ alternatively in my invention.

China clay or kaolin is a uinque material found in large quantities innature (therefore cheap) and readily distinguishable from and havingdefinite advantages over other materials heretofore proposed for thispurpose. In this connection I am aware that the prior art discloses theuse of phosphoric acid as a polymerizing agent, e. g. E. P. 340,515(1930) discloses the use of phosphoric acid on activated carbon orsilica gel and that later patents have disclosed the use of phosphoricacid with materials of a siliceous character which includes diatomaceousearth, kieselguhr and silica gel (artifically prepared porous silica). Iam also aware that certain naturally occurring minerals such as fullersearth, bentonite, montmorillonite and similar mineral adsorbentsubstances which have generally been used as refining agents in thepetroleum industry have been mentioned. However, the use of china clayor kaolin with phosphoric acid has never been disclosed, but none ofthese materials of the prior art has the desirable properties of chinaclay or kaolin as w1ll be apparent from the follow ing characterizationand properties. China clay or kaolin sometimes referred to as alba orwhite bole, terra bole, argilla or porcelain clay is a natural plasticmaterial of remarkably high uniformity in characteristics andproperties. It is composed of silicon, oxygen and hydrogen correspondingto the general formula: Al2Os2SiO22H2O. Its origin is from theweathering of feldspars.

Kaolin is sometimes referred to as an aluminum-silicate but is probablyan aluminosilicic acid.

It differs from the material of the prior art and can be distinguishedtherefrom in the following important respects. Infusorial earth,kieselguhr and silica gel are siliceous materials, i. e. generallycomposed of silica and oxygen (SiOz) and are, therefore, entirelydifferent in composition and properties, e. g. they lack plasticity andthe property of hardening above. Fullers earth is not a true clay, i. c.it lacks plasticity entirely and is readily fusible unlike china clay.Montmorillonite also has very little plasticity. It is composed largelyof hydrogels of silica and is decomposed by boiling acids, e. g. HCl.Bentonite, while highly colloidal, also lacks plasticity. Bothmontmorillonite and bentonite have a much higher silica to alumina ratioand water content than kaolin. They are both amophous whereas kaolinshows a crystalline X-ray structure.

The materials of the prior art are generally of a porous and adsorbentnature whereas kaolin does not possess these properties and, therefore,cannot be classified as an adsorbent.

The plasticity of kaolin and its hardening characteristics areattributable to the interlocking of the minute crystals as well aschemical changes as indicated by low temperature transition points, andthe loss of water on heating.

Having characterized and differentiated china clay or kaolin from thematerials of the prior art, I shall now proceed to show how it is usedand modified compositions may be made and used in connection with thepresent invention.

Concentrations of orthophosphoric acid from approxior pyrophosphoricacid or mixor with P205, metaphosphoric, general a phosphoric acid inwhich phosphorus has a valence of 5 are employed. These are mixed withchina clay (kaolin) preferably adding sufiicient phosphoric acid to thechina clay to obtain the maximum concentration and amount thereof whilepermitting further treatment of the mixture such as forming (byextrusion, etc.), cutting and heating or baking to dry the same. Therelative amounts of kaolin and phosphoric acid may vary roughly between25% to of each, employing the higher proportions with pyrophosphoricacid and mixtures of ortho and P205.

The mixture of phosphoric acid and china clay con-- stitutes a paste ofvarying consistency depending on the temperature of mixing, relativeproportions of the kaolin and phosphoric acid and the kind andconcentration of the latter. Also the application of a relatively smallamount of heat rapidly thickens and congeals the mixture if necessary.The mixture is then formed into pellets, or it may be extruded and cutinto suitable lengths of generally cylindrical or other shapes, e. g.,,42" to /4" diameter and about 4" length, or broken up into thedesirable sizes after drying or baking. The latter process is carriedout at 400 F. to 600 F. for one-half to 2 hours, which is referred to asa drying temperature range by prior art patents as contrasted withcalcining temperatures of 900 F. at 16 hours for the prior art processesemploying siliceous materials and as kieselguhr, infusorial earth andthe like. The reason for the relatively mild treatment in the presentinvention is the natural tendency for the china clay to set at lowtemperatures owing to its plasticity and crystal structure whenmoistened and heated and the process as pointed out previously isessentially one of drying in addition to interlocking of the minutecrystals as well as low temperature transition points and chemicalchanges generally, all of which are not possessed by the prior artmaterials.

When used for polymerizing normally gaseous olefins, the granules orparticles of catalyst are generally placed in treating towers and thegases containing olefins are passed downwardly through the towers attemperatures of 400 to 500 F. and pressures of several hundred pounds,e. g. 100 to 350 lbs. per square inch when employing stabilizer refluxeswhich contain, e. g. to 35% of propene and butenes. With gas mixturescontaining normal and isobutene to obtain mixed polymerization thetemperature may be lower, e. g. 250 to 350 F. with pressure of 500 to800 lbs. per square inch, other reactions may be similarly carried out.

It may also be desirableto introduce some steam during the reaction tomaintain the normal vapor pressure of the catalyst; or the gas may besaturated with water vapor.

To remove carbonaceous or hydrocarbonaceous materials which form anddeposit during the treatment the catalysts are reactivated bysuperheated steam and/ or air or oxygen at temperatures varying from 500F. to 1000 F. dependent on the contractions of oxygen. The steamconcentration may be increased toward the end of the burning off periodand then both steam and temperature are decreased toward the very end.These variations in steam concentration and temperature are directedtowards maintaining the proper moisture content or vapor pressure andstructure of the catalyst.

With regard to the structure and hardness of the catalyst which areimportant in the use and life of the catalyst as well as the rate andtemperature level of drying, I have made several important improvements.

For example, I have found that I can increase the porosity of thecatalyst very much by adding from 1% to 10% based on the kaolin byweight of calcium or magnesium oxides or mixtures of the same or thecorresponding carbonates to the kaolin before mixing in the acid.Preferably the amounts of the materials added should be less than 5%based on the kaolin as they consume acid and in large amounts reduce thehardness and weaken the structure especially calcium oxide. The finalproducts made from a mixture containing calcium oxide are softer andalso tend to take up moisture more readily than mixtures containingmagnesium oxide but on the other hand are more porous. A mixture of thetwo oxides (which ordinarily is found in commercial lime) varying theproportions gives good results. Calcium sulphate may also be used toadvantage. I have discovered also that zinc oxide has a beneficialeffect on the hardness of the catalyst product and ease of drying whenadded to the kaolin to the extent of 1% to 5% and the hardness each ofsetting will be increased to an even greater extent if zinc chloride isalso added to the mixture. The preferred manner of adding the zinc oxideand zinc chloride is as follows. The zinc oxide is first mixed with asmall quantity of the kaolin and a concentrated or syrupy solution isadded. The remaining kaolin admixed with the phosphoric acid is thencombined with the zinc oxide, zinc chloride, kaolin mixture. Thecatalyst resulting from this mixture is hard and dense and can be moreporous by incorporating calcium and/or magnesium oxides to the mixture.

Other additives to the kaolin to improve the properties of the resultingproduct from the viewpoints of quick setting, hardness, structure, etc.are aluminum phosphate (especially if the mixture contains zinc oxide),aluminum or sodium fluorides, copper or zinc silicates and others.

In some cases it has been found that major amounts of kaolin mixed withlesser or minor amounts of other materials such as infusorial or fullersearth and other types of clay imparts its desirable characteristics tothe mixture.

From the viewpoints of economy and control of porosity, hardness andaccelerating setting, I prefer various proportions of calcium andmagnesium oxides taking advantage of the properties imparted by each indetermining the relative proportions of each, e. g. as pointed outpreviously calcium oxide produces a more porous product but is softerand takes up water quite readily but these features are corrected by themagnesium. The corresponding carbonates are useful in increasingporosity because of the evolution of carbon-dioxide.

Other chemical reactions such as alkylation, condensation,isomerization, esterification, etc. may be carried out also with thesecatalysts or modifications thereof.

A desirable oil cracking catalyst results when larger proportions ofkaolin relative to the phosphoric acid are employed. The latter isreduced to a minimum, preferably sufficient only to produce thenecessary binding and structural strength. The phosphoric acid is mixedwith kaolin (together with other components in some cases), andpreferably heated above 400 F. to produce the desired structuralstrength. The catalyst product may be preformed before heating orreduced to desired size afterwards.

The following examples for the preparations and use of these catalystsin polymerizing olefinic gases are illustrative, but are not to beconstrued as imposing undue limitations upon the broad scope of theinvention.

Example 1 65% by weight of weight of kaolin were pyrophosphoric acid and35% by mixed at a temperature of about 325 F. The mixture was extrudedthrough a die of about 7 diameter and cut into lengths of about A". Thepieces were then dried at a temperature of approximately 575 F. forabout two hours.

Example 2 Example 3 65% by weight of a mixture of pyrophosphoric andorthophosphoric acids and 35% of kaolin containing 5% of a mixture ofzinc and magnesium oxides were formed and dried as in Example 1.

Example 4 60% by weight of orthophosphoric acid was mixed with 30% byweight of kaolin and to this mixture was added 10% of a mixture ofkaolin containing about 10% each of zinc oxide and zinc chloride (inaqueous solution) based on the latter mixture. The total kaolin, zincoxide and zinc chloride component was 40%. The mixture was formed anddried at approximately 525 F. to 550 F.

Example 5 65% of ortho and pyrophosphoric acids were mixed with 25% ofkaolin containing 5% by weight of the kaolin of mixed oxides of calciumand magnesium. To this mixture was added 10% of kaolin containing zincoxide and zinc chloride prepared as in Example 4 but about one-half ofthe quantity. The mixture was formed and dried at about 575 F.

Each modifying substance has its own effect and, therefore, they are notto be considered as equivalents. However, with all of the catalystsdescribed one may obtain good yields of liquid products whenpolymerizing gases containing olefins such as propenes and butenes. Theconditions of treatment may be between 400 F. to 500 F. more or lessemploying pressures of several hundred pounds per square inch withstabilizer gases or refluxes containing to 40% of propenes and butenes.With normal and isobutene mixtures, lower temperatures may be employedbut the pressures should be somewhat higher as previously noted.

The efficiency of the process varies not only with the specificcatalysts and operating conditions but also with the concentrations andtypes of olefins. The catalyst efliciency may gradually decrease, e. g.from about 60% to 80% to less than 10% dependent on the length of use ofthe catalyst, the conditions of treatment, etc. The catalyst is finallyreactivated in the ordinary manner by burning off the carbonaceous andhydrocarbonaceous material with oxygen or air and/or steam treatment.

The description and examples are illustrative and are not to beconstrued as restrictive on the broad scope of the invention.

I claim:

individual mineral components comprising an amount of substantially notless than about 25% of the dried mixture and an amount of more than 1%and less than 10%, based upon the weight of the said kaolin, of anothersubstantially water insoluble mineral component selected from the groupconsisting of the oxides of calcium, magnesium and zinc, the carbonatesof calcium and magnesium and the sulphate of calcium.

2. A catalyst composition consisting essentially of a dried mixture of aphosphoric acid and kaolin and an amount of magnesium oxide of more than1% and less than 10% by weight of the kaolin in the said mixture, thesaid kaolin being substantially not less than 25 of the dried mixture.

6 3. A catalyst composition consisting essentially of a acid and kaolinand an and less than 10% by weight of the kaolin in the said mixture,the said kaolin being substantially not less than of the dried mixture.

4. A catalyst composition consisting essentially of a dried mixture of aphosphoric acid and kaolin and an amount of magnesium carbonate of morethan 1% and less than 10% by weight of the kaolin in the said mixture,the said kaolin being substantially not less than 25 of the driedmixture.

5. A catalyst composition consisting essentially of a dried mixture of aphosphoric acid and kaolin and an amount of calcium carbonate of morethan 1% and less than 10% by weight of the kaolin in the said mixture,the said kaolin being substantially not less than 25% of the driedmixture.

6. A catalyst composition consisting essentially of a dried mixture of aphosphoric acid and kaolin and an References Cited in the file of thispatent UNITED STATES PATENTS

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A DRIED MIXTURE OFA PHOSPHORIC ACID AND AT LEAST TWO INDIVIDUAL MINERAL COMPONENTSCOMPRISING AN AMOUNT OF KAOLIN OF SUBSTANTIALLY NOT LESS THAN ABOUT 25%OF THE DRIED MIXTURE AND AN AMOUNT OF MORE THAN 1% AND LESS THAN 10%,BASED UPON THE WEIGHT OF THE SAID KAOLIN, OF ANOTHER SUBSTANTIALLY WATERINSOLUBLE MINERAL COMPONENT SELECTED FROM THE GROUP CONSISTING OF THEOXIDES OF CALCIUM, MAGNESIUM AND ZINC, THE CARBONATES OF CALCIUM ANDMAGNESIUM AND THE SULPHATE OF CALCIUM.